1. Field of the Invention
The invention relates in general to a light emitting diode device, and more particularly to a light emitting diode device with excellent light extraction efficiency.
2. Description of the Related Art
Along with the rapid advance and development of the display technology, the researches and developments of various displays have gained rapidly; meanwhile, the requirements for the functions and characteristics of the displays are also increased. For example, applying phosphors in light emitting diode displays has become a focus in the research of the display technology.
Fluorescent powders are often used in the light emitting diode devices for converting lights. That is, fluorescent powders absorb and convert the light emitted from the light emitting chip of a light emitting diode device into a light with a different wavelength. Suitable types of fluorescent powders can be selected for use in light emitting diode devices according to the needs. Further, the light converted by fluorescent powders can be mixed with the light emitted from the light emitting chip to form a different light. A light emitting diode component that can emit white light is one of the examples.
In a light emitting diode device, when a light emitted by the light emitting chip encounters phosphor particles in the proceeding course, two scenarios may happen. The first scenario is that the angle formed between the light and the surface of the phosphor particles is smaller than a critical angle. Under such circumstance, a scattering effect will happen when the light passes through the phosphor particles and a scattering light will be formed and emitted by the phosphor particles. The scattering light is further divided into a forward scattering light and a backward scattering light. The forward scattering light continues to proceed to the light emitting surface of the light emitting diode device. The backward scattering light is reflected towards to the light emitting chip and transfers into the light energy which being absorbed by the light emitting chip or the light emitting diode device. As a result, an energy loss occurs and the light extraction efficiency of the display is reduced. The second scenario is that the angle formed between the light and the surface of the phosphor particles is larger than a critical angle. Under such circumstance, the light will be totally reflected when reaching the surface of the phosphor particles, and becomes a total reflective light reflected towards to the light emitting chip. Likewise, the reflected light is absorbed by the light emitting chip or the light emitting diode device. As a result, an energy loss is resulted and the light extraction efficiency of the display is reduced. Therefore, how to provide a light emitting diode device with excellent light extraction efficiency has become a prominent task for the industries.